This invention generally relates to the field of battery packs and, more particularly, to those battery packs that communicate intrinsic information over battery voltage terminals.
Many of today's electrical and electronic devices are powered by batteries that require identification of their characteristic. This is specially true for rechargeable batteries where their chemical characteristic plays an important role in their charge and discharge requirement. For example, by identifying battery type, a battery charger may apply a suitable level of charge current for charging the battery. Alternatively by determining safety features of the battery, the charger could stop applying the charge current in time to avoid an overheating condition, which may result in a battery explosion. It is also desired to power an electronic device, such as a cellular phone, by a wide variety of battery types, such as Lithium Ion, Nickel Metal Hydrate, Nickel Cadmium, etc. The battery type identification allows the device to adjust its operating characteristic to accommodate a particular battery type.
Conventionally, various techniques have been used for communicating information between a battery and a battery powered device or a battery charger. Generally, the battery incorporates a non-volatile storage device that stores intrinsic battery information, such as battery type, safety features, model number, etc. In this way, the intrinsic battery information may be communicated over one or more battery terminals according to a predefined communication protocol, which is often a serial protocol. Usually, the device includes a microprocessor for processing the intrinsic battery information received from the battery according to a predefined program.
For communicating intrinsic information, some conventional approaches use dedicated battery terminals, which are separate from battery voltage terminals. For example, many batteries used in portable computer systems include dedicated terminals for communicating intrinsic information to and from the computer system. In smaller portable devices, such as cellular phones and the like, however, the addition of extra terminals complicates mechanical design and adds to manufacturing cost.
Another conventional approach uses the battery voltage terminals to convey intrinsic battery information to a battery charger. In this way, additional battery terminals are not necessary, since the terminals that supply the battery voltage are also used for communicating intrinsic batter information. Using a serial link, intrinsic data relating to a battery identification number and battery usage history may be communicated between the battery and the charger over the battery voltage terminals. Under this approach, the link is provided by a modulated a.c. signal, which is superimposed upon the battery voltage terminals. The modulated a.c. signal consist of a high frequency carrier, for example, 1 MHz, which is frequency or amplitude modulated for identifying two binary states. For example, a frequency modulated a.c. signal may have a first modulating frequency representing a binary state "1" and a second modulating frequency representing a binary state "0." In this way, a collection of logical signals constitute a data sequence representing intrinsic information, which is communicated between the battery and the charger over the battery voltage terminals. In yet another approach, the data sequence may be created by a high power low energy pulse imposed on the battery voltage terminals, to communicate intrinsic information stored in a low impedance battery, such as an acid battery.
Under noisy conditions, however, the conventional methods do not provide reliable communication of intrinsic battery information over the battery terminals. When a battery powered device is turned on, the noise present, due to loading conditions, for example, may distort the communication link with the battery. In order to provide reliable communication, the conventional approaches must transmit the intrinsic data continuously or periodically. This arrangement, however, results in high battery current consumption, which reduces the battery's charged life.
Therefore, there exists a need for a simple way of reliably communicating intrinsic battery information over battery voltage terminals, while consuming very little battery current.